This invention relates generally to vehicles for moving railroad cars and more particularly to railroad car moving vehicles of the type having convertible sets of wheels, one set being track wheels permitting use of the vehicle on the rails of a railroad track and another set being rubber wheels allowing the vehicle to operate on ground surfaces.
Railroad car moving vehicles are used for moving railroad cars without the need for locomotives. Such vehicles are capable of operating both on the railroad track for the moving of railroad cars or on the ground for moving the railroad car moving vehicle between railroad tracks. Such a vehicle is sometimes referred to as a rubber-rail car. When the railroad car moving vehicle is operated on the railroad track, the rubber tired ground wheels are retracted to a position above the rails on each side of the vehicle. When the track wheels are no longer required, the ground wheels are lowered and locked in place so that the vehicle can travel over the ground.
Railroad cars or other railway rolling stock are equipped with knuckle-type couplers. The railroad car moving vehicle also includes knuckle-type couplers mounted on drawbar works cradled in the front and rear ends thereof for coupling engagement with the conventional knuckle-type coupler of an adjacent railroad car. The drawbar works is supported at one end of the vehicle on a pair of radial arms pivotally carried on pivot pins mounted on the vehicle frame at a level below the axle of the driving wheels. The pins serve as a pivot point for the radial arms so that the coupler can pivot up and down at the pivot point. The front end of the drawbar works is supported on the vehicle frame above the driving wheel axle. A hydraulic ram, pivotally connected between the vehicle frame and drawbar works, swings the drawbar works about its radial arm pivots to raise the drawbar works relative to the frame.
Upon coupling the vehicle to the railroad car, a portion of the weight of the railroad car is transferred to the vehicle by lifting the car coupler. The railroad car has a suspension system with springs and a large pin which extends downwardly towards the axle of the railroad car. The axle is separate from the car itself. Even though the weight is lifted off the axle of the car by the vehicle, the wheels on the axle of the railroad car continue to engage the track. The vehicle uses a portion of the railroad car weight to increase traction of the propelling force of the vehicle. Since the tractive force is borrowed from the weight of the railroad car to be propelled, the vehicle itself may be relatively light in weight.
The coupling between the drawbar works and the car coupler lifts the railroad car causing the drawbar works to support a portion of the weight of the railroad car. This weight is transferred back to the frame of the vehicle. The amount of initial loading of the vehicle frame from the railroad car is controlled by extension of the hydraulic ram.
The railroad car moving vehicles of the prior art have several disadvantages. In particular, prior art vehicles experience excessive shaking, vibration and shock causing the vehicles to lose traction and thus acceleration. Further, the ride is uncomfortable for the driver.
The prior art vehicle is all rigidly mounted. There is merely a mechanical linkage between the wheels of the vehicle and the railroad car itself. When the coupler on the vehicle lifts the railroad car and supports a portion of the load, the load is transferred to the wheels of the vehicle and the coupler takes all of that load. This load may actually split the foundation of the coupler.
When the vehicle is coupled to the railroad car, a severe loading impact is absorbed by the vehicle coupler. The prior art couplings are constantly being damaged by the shock load during the coupling operation. Often, the roller bearings break. Some prior art couplers have rubber mounted in the coupler itself. A round rubber donut is installed around the coupler spindle. Such a rubber element has some effect but still does not substantially reduce the shock.
The rigid mounts of the prior art vehicle creates a steel path from the railroad car coupler to the ground. As the vehicle and railroad car travel on the track, any interruptions in the rails over which either the railroad car that is being lifted or vehicle passes, cause steel constrained dynamics to occur. Steel is unforgiving in the absorption of energy. Thus, the energy and load pass right to the frame of the vehicle. This causes a shaking, vibration or shock to the vehicle. The shock of connecting the railroad car only occurs once, but as the vehicle travels over the rails in a steel system repeated vibrations occur to the vehicle making it uncomfortable for the driver and a maintenance problem for the vehicle.
Shock is also caused when the drive is over-loaded and the wheels slip. The slippage of the steel wheels on the steel track causes a steel on steel slip condition which produces a shock to the vehicle. The slippage of the wheels causes an up and down movement or vibration. This vibration is felt by the driver of the vehicle.
Normally, the vehicle is used only to move a single string of railroad cars and generally does not have a car coupled to both ends of the vehicle. However, often the vehicle is damaged because the vehicle has been attached to a railroad car at both ends.